Assessment of the regional source contributions to PM_(2.5) mass concentration in Beijing

A source apportionment tool,ISAM （Integrated Source Apportionment Method）,coupled with a regional air quality modeling system,RAMS-CMAQ （Regional Atmospheric Modeling System and Community Multiscale Air Quality）,was applied to simulate the major aerosol components （sulfate,nitrate,ammonium,black carbon,organic carbon,dust,and sea salt） and investigate the impact of local and regional sources on the PM2.5 （particulate matter with an aerodynamic diameter less than 2.5 μm） mass concentration over the North China Plain （NCP） in July 2016.The simulation results indicated that the high mass burden of PM2.5 mainly appeared in the south part of Hebei and west part of Shandong.The PM2.5 particles emitted from Beijing and Tianjin were just concentrated in the local area,but Hebei and Shandong were the dominant source over the NCP.Focusing on Beijing,the local contribution was just 20%-30% due to the emissions control strategies executed in recent years in Beijing.The pollutants derived from Hebei and Shandong were major contributors,providing more than 25% and 10% to the PM2.5 mass concentration in Beijing,respectively.Moreover,the surrounding regions showed larger contributions against the pollution background.The contribution percentage from Hebei and Shandong increased in both cases when the air quality became worse.Thus,it is suggested that comprehensive control strategies should be implemented based on coordinated control of emissions at the regional scale in Beijing,especially during pollution periods.

将先进的在线源追踪模拟模块ISAM与空气质量模式系统RAMS-CMAQ耦合,对2015年7月华北地区主要气溶胶物种(硫酸盐、硝酸盐、铵盐、黑碳、有机碳、沙尘和海盐)进行模拟,并且深入探讨了不同地区排放源对PM_(2.5)质量浓度的贡献特征。模拟结果显示PM。2.5质量浓度高值主要出现在河北省南部和山东省西部北京和天津市的排放源对PM_(2.5)质量浓度的贡献主要集中在本地,而河北和山东省则为华北地区PM_(2.5)质量浓度的主要贡献者。就北京市而言,由于近年执行了多项减排措施,目前该地区的本地贡献占20%-30%。而河北和山东省是北京市PM_(2.5)的主要区域传输贡献者,分别可超过25%和10%。此外,在污染背景下周边地区传输贡献的比重更大。当空气质量恶化时,河北和山东省的传输贡献比例均有所提升。因此,建议在污染期间,应重点基于对区域尺度的排放源开展协同控制,制定综合的减排措施方可进一步降低北京市的PM_(2.5)质量浓度。